Leybold Braun Electroscope, 5A22.10

Rub rod with fur, touch rod to knob on top of electrometer. Full-scale needle deflection 1500V.

On dry days, full-scale deflection is easy to achieve with rod and fur, or even by putting your finger on the knob and shuffling your shoes on the floor. On wet days, it is much more difficult to achieve an impressive deflection.